1. Field of the Invention
This invention relates generally to a process for preparing carriers for integrated circuit chips and the like and, particularly, relates to such a carrier including a flexible film base, such as a polyimide.
2. Description of the Prior Art
It is conventional practice to provide a polyimide tape, such as is known by the trademark Kapton obtainable from DuPont. In this connection, reference is made to the patents to Marley, Nos. 3,390,308, Aird, 3,689,991, Brummett et al., 3,937,857, and Hamlin, 3,968,563.
When using such a polyimide carrier, it is necessary to remove the polyimide layer surrounding the bumps of a bump circuit as well as the sprocket holes which are conventionally placed on both sides of a lead and bump circuit to provide precise registration with the semiconductor chips.
In accordance with the present invention, this is effected by a chemical milling process, not disclosed in these patents. Preferably the chemical milling is effected in a plasma reactor utilizing oxygen (O.sub.2) and carbon tetrafluoride (CF.sub.4), in the manner disclosed and claimed in the patent of Phillips, U.S. Pat. No. 4,012,307, assigned to the assignee of the present application.
Various processes for preparing such chip carriers have also been disclosed in the past. In this connection, reference is made to the patent to Galli et al., U.S. Pat. No. 3,781,596. FIG. 10 of this patent does refer to a process for preparing a bump circuit over a layer of polyimide. The bump circuit may then subsequently be provided with a layer of gold, aluminum, copper, or the like.